1. Field of the Invention
The present invention generally relates to an angular velocity sensor, and more particularly, to an angular velocity sensor having a tuning-fork oscillator.
2. Description of the Related Art
An angular velocity sensor is a sensor that senses angular velocity while the object is rotating, and is used in systems for preventing camera shakes, for navigating vehicles, for controlling positions of vehicles or postures of robots, and the likes. Japanese Unexamined Patent Publication No. 2001-165664 discloses an angular velocity sensor that uses tuning-fork oscillators. In this angular velocity sensor, two tuning-fork oscillators are bonded directly to each other, so that the generated charges have the opposite signs from the charges generated in each other tuning-fork oscillator. In this manner, the driving efficiency is increased by adjusting the electrode arrangement.
As angular velocity sensors have been becoming smaller, tuning-fork oscillators have also been becoming smaller. With smaller tuning-form oscillators, the driving efficiency becomes lower. When the driving efficiency becomes lower, the amplitude of driving oscillations becomes smaller. When angular velocity is applied, the amplitude of sensing oscillations generated by Coriolis force becomes relatively smaller, and therefore, it becomes difficult to sense the angular velocity.
For instance, the angular velocity sensor disclosed in Japanese Unexamined Patent Publication No. 2001-165664 requires the process of bonding tuning-fork oscillators so that the generated charges have the opposite signs. As a result, the number of manufacturing procedures becomes larger, and the production costs become higher. Further, the driving efficiency becomes lower due to bonding misalignment in the bonding process.